But they moved higher again on Friday ahead of a three-day holiday weekend in the US. About a quarter of US crude oil installations are located in the Gulf of Mexico.

“The focus is likely to remain on Tropical Storm Gustav and potential supply disruptions during the weekend and earlier next week,” Sucden analyst Andrey Kryuchenkov said.

As Gustav advanced, oil companies were pulling employees off installations.

Royal Dutch Shell PLC has evacuated nearly 670 workers. The company said production will be affected. BP PLC was also removing personnel from the region, while Exxon Mobil said it was bracing its structures for heavy wind and rain.

Transocean Inc, the world’s largest offshore drilling contractor, said on Thursday it had evacuated about 190 workers from five of its 11 offshore drilling rigs in the Gulf. Transocean has 1,550 workers in the region.

The threat of Gustav raised grim memories of the 2005 hurricanes Katrina and Rita that damaged or destroyed about 165 oil platforms of the some 4,000 located in the Gulf.